Probing the chiral nature of electromagnetic fields surrounding plasmonic nanostructures

We investigate the chiral properties of near fields around plasmonic nanostructures and their relation to the electromagnetic chirality C. By combining chiral metal nanoparticles with achiral dye molecules and measuring the circular polarization dependence of the enhanced photoluminescence, we find a correlation between the dissymmetry of the luminescence enhancement and the calculated values of C. These effects are strong (~{10}^{{-}1}$), despite the weak circular dichroism of the particles (${~}10^-5). We further show that C represents the chiral selectivity of the near-field coupling between an emitter and a nanoantenna.